70 ON POTASSIUM AND SODHJM. 



I|i09» p. 57*. Perhaps after hsivin^ carefully perused 

 that note, in which the followin2j sentence occurs. — ** So- 

 •* (lium appears to be almost insolnbfe in hidrpgen^ and 

 ** this seems to be one reason, why \t cannot he oht dined., 

 ** except in very minute quantities, in the experiment with 

 ** the gunbarrel."— The reader may. be rather surprised on 

 turning to jp, 503 of Mr. Dalton's new system, to I'md the 

 fbllowing, — ^^" Though Mr. l>avy*s original method of ob- 

 *• taining sodinm by Voltaic electricity is the most instruc-^ 

 *^ tive, as to the nature of the new product, yet thwt of 

 ** Gay-Lussac and Thenard is the niost convenient^ when a 

 *' gtta?if2/y of the article is required. That is, to pass the 

 *'' vapour of redhot hydrate of soda over iron turnings, in a 

 ** gunbarrel heated to whiteness,^'' — Mr. DaUon thus recom- 

 mends a process for procurinj^ sodiurn by wholesale, which 

 IVIr. Davy informs us will afford it only in very minute 

 (Quantities. Which of the two is to be taken as authority 

 in this case? 

 Another To follow Mr. Dalton a little farther in his arguments 



-areumept of f^,, ^^^ compound ' natuTe of potassium, he sayy, *' The 

 Mr. DaUon , . ^ . i • i • i • , i- , i 



from the light- ** levity of jt, combined with its volatility at a lovv red 



nessof potas- ti beat, agrees with the notion of its being potash and 

 * *' hidrogen, or potas^etted hidrogen, resembling the other 



" known compounds, of sulphur, phosphorus,- charcoal, 

 already an- ** arsenic, &c. combined with hidrpgen." As to its low 

 swered by Mr. gpg^j^P gravity being a proof in favour of Mr. Dalton's 

 idea, it is answered by Mr. Davy in his paj^r " on the 

 decomposition and composition of the fixed alkalis,'* p. 31 

 of the Philosophical Transactions for 1808t,'jn which 

 (haying stated that it was the opinion of most of the philo- 

 sophical gentlemen, whom he had consulted, that the new 

 substances should be called metals) he observes, that their 

 letily is not sufficient reason for making them a new class, 

 i'ov there are remarkable differences in their respective spe- 

 cific gravities among the metals, as for instance, between 

 platina and, tellurium, the former being nearly four times 

 heavier tKah tlie latter,— "^aod in the philosophical division 

 ♦* of Che classes of bodies, the analogy between the greater 



f Journal, vol. XXIII, p. 256. • t Ibid, toI. XX, p. 521, 



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